Quick microwave assembling nitrogen-regulated graphene supported iron nanoparticles for Fischer-Tropsch synthesis

Facile preparation of highly efficient iron-based catalysts is vital to improve the performance of Fischer-Tropsch synthesis (FTS), a sustainable process for converting non-petroleum carbon resources to valuable hydrocarbons. In this work, a convenient preparation for nitrogen-regulated graphene supported iron nanoparticles, with the assistant of microwave treatment, was developed. Thereinto, the nitrogen-containing groups in graphene support were introduced by NH3·H2O treatment. By comparison with ordinary calcination, microwave treatment could significantly shorten the heating time to few seconds, and promote the reduction of iron species. The existence of a small number of nitrogen-containing groups could effectively anchor iron species, and improve the dispersion of iron species. Meanwhile, the duration length of NH3·H2O treatment time could regulate the content of N configuration (pyridinic-N and pyrrolic-N). The size of supported iron species from 120 nm to 10 nm could be well controlled via increasing microwave time from 0 to 14 s. For N-regulated graphene supported iron catalysts, evenly dispersed small particles of iron species, improved surface reduction behavior and reasonable N configuration all promoted FTS. Under relevant industrial conditions (320 °C, 2.0 MPa, 5 g h mol−1), the optimized 15%Fe/AG(12 h)-W(10) catalyst achieved CO conversion as high as 97.2% and C5+ selectivity of 40.0% while maintaining a mild CO2 selectivity (28.2%). The superior preparation and catalytic performance disclosed that the catalyst could be one of ideal candidates for industrial iron-based FTS catalysts in future.